The present invention relates to a contact-disk system having a rotatable contact disk and a plurality of contact elements, the contact disk having a plurality of paths and each contact element being assigned to one path. The present invention also relates to a method for controlling a windshield-wiper motor using a contact-disk system having a rotatable contact disk and a plurality of contact elements, the contact disk having a plurality of paths and each contact element being assigned to one path. Furthermore, the present invention relates to a windshield-wiper motor which comprises a contact-disk system having a rotatable contact disk and a plurality of contact elements, the contact disk having a plurality of paths and each contact element being assigned to one path.
Conventional windshield-wiper devices may include contact-disk systems as well as methods for controlling windshield-wiper motors for cleaning of motor vehicle windshields. The windshield-wiper devices may be operated by a switch which may be located in the vehicle interior, the switch being implemented, for example, as a steering-column switch. By operating the steering-column switch, the windshield-wiper device may be shifted from a switched-off state to at least one operating state. The operating states may be implemented by a plurality of windshield-wiper speeds and an intermittent control.
To ensure that the windshield wipers do not come to rest in an intermediate position when the windshield wiper is switched off by the steering column switch, but instead are properly guided back to park position, contact-disk systems may be used. Such contact-disk systems may maintain a closed circuit, in which the windshield-wiper motor operates, until the windshield wipers have reached the park position.
FIG. 1 shows a contact disk 110 which may be used in a conventional contact-disk system. A contact disk 110 of this kind may be installed in generic windshield-wiper motors in such a manner that it rotates in synchronism with the windshield-wiper motor. Contact disk 110 establishes contact with three contact elements, which in each case glide on one path of contact disk 110. A first contact element glides on outer path 120, which has a gap. A second contact element glides on inner path 122, which is implemented as a short path, and a third contact element glides on a center path 121, which is continuous. Such a construction may maintain a current flow in all motor settings, except for the end position and in an area approaching the end position. This may be achieved by a contact element, which is connected to the positive pole of the battery, gliding on outer path 120. A contact element gliding on center path 121 is connected to the wiper motor. Therefore, a current flow from the positive pole of the battery to the wiper motor is maintainable as long as the first contact element glides on a conductive region of outer path 120. The current flow may only be interrupted when contact disk 110 has rotated to the point where the contact element is located in the gap in outer path 120. Due to the inertia of the motor, the contact disk continues to rotate despite the interrupted current flow. However, this further rotation may come to an end when the conductive region of short, inner path 122 connects with a contact element. This contact element is switched such that the motor is short-circuited and may be actively braked in this manner.
Due to the three paths of a conventional contact disk, it may have a certain minimum size. However, in the case of windshield-wiper motors it is desirable to achieve an overall size that is as small as possible, and, therefore, in particular also a small size of the contact disk. A small size of the contact disk may also be desirable in the production of windshield-wiper motors, in particular in rear-wiper motors with oscillating gears, where the contact disk may be required to be arranged with the contacting on the opposite side with respect to the oscillating gear. For this reason, the windshield-wiper motor may be required at present to be rotated on the assembly line during production, which may make the production process expensive.
The present invention builds on the conventional contact-disk system in that the contact disk may have two paths and in that two selected contact elements of the plurality of contact elements may always be at the same electrical potential and glide on the same path. In this manner, an electric current flow may be maintained, with a two-path contact disk, until the park position of the windshield wiper is reached or until shortly before the park position has been reached. Because the contact disk may require no more than two paths it may have a smaller size and a smaller radial overall width, which may be desirable with respect to the mentioned overall size of the windshield-wiper motor and in view of the manufacturing process.
The selected contact elements may glide on a first path, which may have an electrically conductive and an electrically insulating area, and at least one contact element of the selected contact elements is connected to the electrically conductive area. If the windshield-wiper motor is switched off by operating the steering-column switch, an electrical connection to the wiper motor may be maintained at least via one of the selected contact elements, since at least one of the selected contact elements may always be in contact with the electrically conductive area of the first path.
The electrically insulating area of the first path may be implemented by a gap in a conductive path, and the selected contact elements may have a spacing that is larger than the gap of the first path. Therefore, given a circular contact disk, the electrically insulating area may be realized by a cut-out with radially extending boundaries. If the opening angle of this gap is less than the clearance angle of the selected contact elements, it may be assured in this manner that one of the selected contact elements is always in contact with the electrically conductive area of the first path.
A first, additional contact element may glide on the first path. This first additional contact element may be used to maintain an electrical connection between the contact disk and the positive pole of the vehicle battery. Therefore, even when the steering-column switch is in the off-position, an electrical connection mat be maintained between the positive pole of the battery and the motor via the first additional contact element and at least one of the selected contact elements. Only when the first additional contact element leaves the electrically conductive area of the first path and is located in the insulating area of the first path, may the current flow be interrupted.
A second path may have an electrically insulating area and an electrically conductive area. A second additional contact element may glide on the second path. This contact element may be used to realize an electrical short-circuit of the motor and to actively brake the motor in this manner once the park position has been reached.
The gap in the first path, the electrically conductive area of the second path, the first additional contact element and the second additional contact element may be arranged with respect to one another in such a manner that a state exists in which neither the first additional contact element nor the second additional contact element are connected to an electrically conductive area of the first path and the second path, respectively. Although the current flow in the electrical circuit of the windshield-wiper motor may already be interrupted, the motor and the contact disk may still continue to rotate, due to their inertia. During this phase the motor speed may be reduced, and an active braking of the motor may only occur, due to the electrical short-circuit, when the second additional contact element makes contact with the electrically conductive area of the second path.
The angular range, which may be covered by the electrically conductive area of the second path, may be less than the angular range that is covered by the electrically insulating area of the first path. As a result, the first additional contact element may have already left the conductive area of the first path due to the rotation of the contact disk, while the second additional contact element may have not yet reached the conductive area of the second path. Therefore, the motor may be neither actuated nor actively braked in this intermediate state. The motor may continue to rotate due to its inertia, with the rotational speed decreasing, however. Only when the electrically conductive area of the second path makes contact with the second additional contact element, may the motor be finally braked.
These contact elements may be contact springs. In this manner, a reliable contact between the contact disk and the contact elements may be established.
The present invention may build on a conventional method in that a contact-disk system according to the present invention may be used to control a windshield-wiper motor. In this manner, a contact-disk system according to the present invention may be implemented by a control method.
In an exemplary method according to the present invention it may be desirable if a switch connected to the contact-disk system is operated and if a rotation of the contact disk is maintained until the second additional contact element is connected to the electrically conductive area of the second path. Thus, the control method may allow the windshield wipers to be guided from one operating position to a park position in a reliable manner.
In this context, prior to connecting the second additional contact element to the electrically conductive area of the second path, the connection of the first additional contact element to the electrically conductive area of the first path may be interrupted. Although the electrical connection of the motor and the battery may already be interrupted during this created intermediate state, rotation may still occur nevertheless, due to the inertia of the involved components, although the rotational speed of the motor may decrease. Only when the second additional contact element contacts the electrically conductive area of the second path may an active braking of the motor occur.
The present invention may build on a conventional windshield-wiper motor in that it may have a contact disk according to the present invention. As a result, the windshield-wiper motor may implement desired features of a contact disk according to the present invention and an exemplary method according to the present invention. A windshield-wiper motor may be manufactured that has a reduced size.
The present invention may be based on a recognition that, by an appropriate arrangement of contact elements and a suitable geometric design of a contact disk, the functions of a three-path contact disk may be realized, as it may be used in conventional windshield-wiper motors, or by two-path contact disks. Therefore, windshield-wiper motors according to the present invention may also be produced in smaller sizes. The manufacturing process, in particular, may be simplified since a rotation of the motor on the workpiece-carrier of the assembly line may no longer be required.